Like anything else relying on a battery, you car key fob can die—often at the worst time. Thankfully, these batteries are easy to replace.

If your key fob isn't working, it probably needs a new battery.

There’s usually a mechanical key hiding inside the key fob for cars with push-button start systems, so you can still unlock your door if the car battery or your fob battery runs out of juice.

In this primer on how to replace a car key fob, Consumer Reports says getting another high-tech key fob can be a pricey proposition.